The research objective in this R2l and R33 phased application is to advance the technology utilized in the diagnosis and delivery of localized therapy in the treatment of prostate cancer through the development of instrumentation allowing for improved and reproducible navigation and controlled probe insertion into the prostate gland. The deliverable is an accurate mechanism for performing precise image-guided procedures such as biopsy, brachytherapy, cryosurgery, hyperthermia, interstitial laser therapy, focused ultrasound and microwaves, chemotherapy, gene therapy, or other novel procedures. We propose the development of a new instrument for precise image-guided intervention. Even though this proposal's application relies in the urologic field, the proposed system applies to a large variety of other specialties. This application restricts the application range to the diagnostic and treatment of the prostate since urologic applications are our main domain of interest. The centerpiece of research is a compact image-guided robotic system which can be used with standard and modern medical imaging equipment. The novelty of the system relies in its compatibility with multiple imaging modalities, such as fluoroscopy, ultrasound, computer tomography (CT), magnetic resonance imaging (MR), and spectroscopic imaging (MRSI). This allows not only for performing procedures with the imager of choice but also for using cross-platform, combined imaging modalities. An intense research effort is presently focused on the development of novel methods for advanced imaging and improved visualization. In contrast, the instrumentation used for image guided navigation and therapy delivery advanced modestly. Needle procedures are typically performed freehand or with a "template" device under transrectal ultrasound guidance. At present, no mechanical device exists for controllably and repeatedly access the prostate with a precision comparable with that of modern medical imaging systems. While the medical community is still divided about the best treatment modality of prostate cancer, there is undivided agreement about the poor specificity and predictability of the currently used prostate access techniques. Enhanced MR imagery provides uncontested tissue contrast and image quality, which ought to be used for guiding biopsy and localized therapy. This goal requires miniature, extremely high dexterity robots that are able to operate inside the magnet of MR scanners, which may be "open" or conventional closed bore systems. This task also demands a quantum leap in the current technology of mechatronic devices and clearly leads medical robotics into the next millennium. We propose to develop an instrument that could exploit the most advanced imaging methods for implementing the results obtained by urologists, oncologists, radiologists, radiotherapists, and biomedical researchers into clinical use. It creates means for measuring the local extent of the disease, for performing controlled biopsy and therapy delivery through advanced image-guided navigation and control. In conjunction with the recent citrate/choline ratio methods of tumor localization under MRSI, for example, this multi-application system could be used to perform precise tumor-centered biopsy procedures. The main research challenge relies in the robot compatibility with multiple imaging systems, especially the conventional MR imager. Innovative engineering research will address design miniaturization, adequate material selection and manufacturing. The mechanical part, which will operate within the conformed space of the imager in close proximity of the prostate, will be radiolucent, nonmagnetic, dielectric, and will provide means for safety and sterilization. For this, the system, including the motors, will be constructed of materials such as plastics, carbon fiber composites, ceramics, glasses, and rubbers. The use of electricity in the imager's room will be eliminated by using optical sensors and pneumatic/hydraulic motors while all control equipment will be located in the control room of the imager.